CETOTOLITES. 527 
An entire specimen of this compound bene has not yet 
been obtained from the Red-crag; nor is it likely that it 
should be. Almost all the fossils of this formation show 
the action of surf-waves or breakers; those under con- 
sideration appear to have been dislodged from a subjacent 
eocene deposit ; and as the massive petrous bone and the 
tympanic bone of the Cetacea adhere to each other natu- 
rally by only two small surfaces, they would hardly escape 
being broken asunder under the operation of such disturbing 
forces. 
All the specimens which were submitted to me by Pro- 
fessor Henslow consisted of the tympanic portion only, 
and I have as yet seen but one specimen of the rugged 
petrous bone; it is now in the collection of Mr. Brown, of 
Stanway. The tympanic bone may be readily recognised 
by its peculiar conchoidal shape and extremely dense tex- 
ture; the recent bone breaking with almost as sharp a 
fracture as the petrified fossils. 
None of these tympanic fossils are entire: the thin 
brittle outer plate which bends over the thick, rounded, 
and, as it were, involuted part, like the outer lip of such 
simple univalves as the Bulle and Leptoconchi, is broken or 
worn away in the best specimens, all of which are rolled 
and waterworn. I was at once led by their size to the 
largest of the existing Cetacea for the subjects of com- 
parison, as the Grampus, the Hyperoodon, the Cachalots 
(Physeter), and the true Whales (Balenoptera and Balena). 
‘Two or three of the specimens were fortunately sufficiently 
entire to show the form of the tympanic cavity bounded by 
the overarching plate, with the proportion and direction of 
its anterior or Eustachian outlet, and most of them had the 
opposite or hinder extremity entire. They were thereby 
seen to differ from the tympanic bones of the Delphinide, 
